This proposal involves the development of a simple assay for measuring functional approximately-proteinase inhibitor levels in human tissues. The procedure utilizes the fact that incubato of excess porcine pancreatic elastase with either plasma or serum samples will result in complex formation with functional approximately 1-proteinase inhibitor in these fluids. Residual enzyme activity can then be calculated and a determination made as to inhibitor levels present in the original sample. The techniques to be utilized should provide a rapid and reliable procedure for the early screening of individuals with a genetic deficiency in approximately 1-proteinase inhibitor and, thereby, reduce the risk of development of familial emphysema in this segment of the population.